Conservative MPs calling for David Cameron to be removed as party leader are "daft", former leadership contender David Davis has said.
The Tory MP and former minister, who ran against Mr Cameron to be party leader in 2005, warned now is "not a time for introspection".
Mr Cameron's leadership is facing serious scrutiny due to the poor state of the national finances.
He is also under continuing pressure from eurosceptics from within his own party for a referendum on Britain's membership in the European Union.
On top of this, there is growing concern among Tories about whether Mr Cameron can deliver an outright majority at the next general election.
Speaking on the eve of the party's conference in Birmingham, Mr Davis told Parliament's The House magazine: "Writing letters is daft. We are in the middle of a national crisis in economic terms. It is not a time for introspection."
According to the Spectator last month, a group of 14 Tory MPs wrote to Graham Brady, chair of the backbench 1922 committee, asking for a leadership challenge.
However, they fell short of the 46 MPs required to trigger a contest.
Mr Davis has urged the Prime Minister to "have a plan" on Europe. "At the moment I don't have a feeling that the party or the Government knows explicitly where it's going," he said.
"The explicit answer to the European issue, whether it's eurozone or the more general European membership issue, is a big renegotiation and multiple referendums."
Mr Davis also touched on the risks to the Conservatives posed by the UK Independence Party (UKIP).
He said: "UKIP's appeal is not just about Europe. They basically present themselves as an alternative Conservative party. Whether it's law and order or whether it's green policy. It's like a Conservative primer. We want to watch it."
In another interview with The House, newly-appointed Justice Secretary Chris Grayling said the party needed to make "symbolic statements between now and the next election" on issues including Europe to appeal to its core supporters.
"I do not believe we can win the next election if we have not got our supporters behind us," he said.
"To win a general election, you have got to have people who are broadly in the Conservative family together united behind us. I think that's something we have to work to do."
Meanwhile, Lord Ashcroft argued the party needed to do more to attract potential Conservative voters.
A private poll by the Tory peer and former deputy chairman of the party found that up to 15% of the electorate is made up of what he called "suspicious strivers" - people with aspirations, but who are concerned hard work counts for less than connections.
He said: "While they can see the Tories are for people who have achieved material success, it is not clear we are for people like them who do the right thing but have little to show for it. Cameron's task next week is to show that we are."